The compound that can work both as an oxidising and reducing agent is

$H_2O_2$ reacts as a reducing agent with:
$(I)$ $KMnO_4$
$(II)$ $K_2Cr_2O_7$
$(III)$ $Ag_2O$
$(IV)$ $HNO_3$

The $pH$ of a solution of $H_2O_2$ is $6.0$. Some chlorine gas is bubbled into this solution. Which of the following is correct?

The volume (in $mL$) of $10$ volume $H_2O_2$ solution required to completely react with $200 \ mL$ of $0.4 \ M \ KMnO_4$ solution in acidic medium is

How many millilitres of $20$ volume $H_2O_2$ solution is needed to react completely with $500 \ mL$ of acidified $1 \ N \ KMnO_4$ solution?

Which of the following is $NOT$ true for the electrolytic preparation of $H_2O_2$?